This invention is generally directed to improvements in projection television systems. It is particularly directed to an assembly for holding three CRTs in optical alignment with a screen on which the CRT images are projected.
As those skilled in the art of projection systems will recognize, it is extremely important that the three CRTs which develop projected images be held in proper alignment with their intended optical axes. Deviations from proper alignment result in a distorted image on the projection screen. Sometimes, even the usual electronic image alignment circuitry is incapable of properly compensating for such distortions. Moreover, the use of electronic alignment circuitry to compensate for optical and mechanical alignment difficulties is time consuming and requires an undesirably high level of complication in the electronic circuitry.
Conventional CRT holding assemblies use metal clamping rings, brackets and the like to hold all three tubes and their associated lenses. Generally, the three tubes and their lenses are spanned by a single bracket. To replace a defective tube, the bracket must be loosened, thereby allowing the non-defective tubes to be inadvertently and unknowingly moved from their factory-aligned positions. Once this occurs, it is very difficult to determine whether the resultant image misregistration is attributable to electronic errors or optical registration errors. Hence, the misregistration is frequently compromised by resetting the electronic alignment circuitry, but its range and capability are normally insufficient for this purpose.
These and similar problems with conventional CRT holding assemblies render CRT alignment and replacement unsatisfactorily difficult, and frequently result in compromised performance.